In order to observe the processes in the brain, it is known to carry out an examination with the aid of functional magnetic resonance and PET recordings. During such examinations, image data are acquired usually in the change from the normal state and during various forms of brain activation, that is to say in various activity states, and the results are compared. It is, in particular, also possible here to carry out in addition to the functional magnetic resonance recordings diagnostic magnetic resonance recordings by which a spatial assignment of the activity centers is then enabled. If various activity states distinguish, for example, a state without external stimulation, frequently termed “baseline” or resting state, as well as a state influenced by an optical, acoustic or haptic stimulation or a movement undertaken by a patient, frequently termed activation, a recording operation will be performed during several of these activity states.
In order to avoid settling times and, in particular, to have enough PET tracer available in the PET case, there are determined within these activity states time windows in which, under normal circumstances, optimum results are attained that are then scarcely influenced by settling processes or transition phases. The time intervals between the time windows suitable for the acquisition themselves form time windows and are frequently termed “rejects”, since these images are not fed to the evaluation. The sequence of time windows is denoted in technical language as a “paradigm”.
Such functional brain examinations are currently carried out sequentially, that is to say each modality on its own. The resulting images and functional data are subsequently fused in a findings and postprocessing application. Both the increased time requirement owing to the separate examinations and the associated difficulties for the patient, and the time spacing between the application of the individual modalities are disadvantageous here. Since magnetic resonance and PET images cannot be recorded simultaneously, the conditions can differ, and the functional brain processes cannot be simultaneously correlated. Furthermore, it is necessary to take heed of the spatial inaccuracy in the subsequent image fusion and/or image correlation.
So-called hybrid modalities have recently been increasingly proposed, consideration also having been given, in particular, to the connection of magnetic resonance and PET installations. Such units particularly enable a simultaneous and isocentric measurement of magnetic resonance and PET data.